They have to do this from time to time - reset the meta. I don't think the changes will neuter HE that much, not really the Alchemist - sure they are nerfs but it could have been worse for the characters. It should alter the top of the arena boards for sure. I have not been using HE in my defence - stuck with Benjamin Breeg and he is doing fine enough.
I just wonder if they would ever consider making each arena rotation have different team rules like the waves of gauntlet - just to change it up for us all. So have a Gunner/Assassin/Warrior/Magus/Sentinel week rotation. Or a natural 1/2/3/4/5 star week - it would at least shake it up and surely it is quite easy to implement like they have done on gauntlet. There may be less need then for OP characters getting hit with nerfs after a month or two.
Probably too much to ask as I think the team is so small that they really just do not have the staff to look at many things at the same time. They have probably all had to do overtime on the set up for the xmas events and of course getting Night City live.